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Old 24th February 2008, 07:27 AM   #1
diyAudio Member
Join Date: Apr 2005
Location: Spain
Default Powering relay coils using +/- voltage

Hi all,

Searching for info about relay-switching in this web I’ve found this post (of Upupa Epops):

“Induction from relay coil to signal line is not crazy, but you must use good stabilised voltage and coil must use + / - voltage ( 2 . 12 V instead 1 . 24 V ). Relicts of hum on both ends of coil winding are typical together in phase oposite, so induction of hum is disregarded”

I have a good dual mono PSU that puts 24Vdc, that is converted to +12/0/-12Vdc by a rail splitter in each channel of the preamplifier. I thought I had to power the relays using the PSU two-pin 24Vdc output (with 24Vdc relays), but according the above quote it would be better to use 12Vdc relays powered from the rail splitter +12/0/-12Vdc output. Is this correct? If so, how to wire the 12Vdc relays from the +12/0/-12 output socket pins? Just connecting the “+12V” to the (+) coil terminal in the relay and the “-12V” to the (-) terminal, leaving the rail splitter “0” output pin disconnected?

BTW, I have read that Omron low-level signal relays (like G5A or G6A series) are good, but have you any experience with Axicom Palladium-Ruthenium IM02 relays or Matsushita NF2EB relays?

Thank in advance for your help

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Old 25th February 2008, 02:56 AM   #2
diyAudio Member
Join Date: Dec 2007
Location: Phoenix, AZ
Buenos Dias Jose, Your description of connecting the +12v to the + terminal of the relay and -12v to the - terminal of the relay, and leaving the 0v common terminal not used for the relays is correct. The relay coil doesn't care how it gets the 24vdc difference across it, it just wants to see a 24v potential across it's terminals for it to work. As far as being better or worse, that would require some experimentation. Upupa Epops comment has merit, there will be a higher degree of hum rejection, but if you have a well designed 24vdc power supply, this should be unnoticeable. I would suggest that you try connecting power to the relays both ways, then decide if you hear a difference. Also, please report your findings back to the other members here. It helps us all learn.


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Old 27th February 2008, 06:51 PM   #3
diyAudio Member
Join Date: Apr 2005
Location: Spain
Default Thank you

Thank you for your answer, Dave

I'll connect the "+" and "-" coil terminals to the +12V and -12V pins of the 3-pin "DC-in" header that powers each channel of the preamplifier, leaving the "0"V pin disconnected from the relays, although this 3-pin header will supply with the full +12/0/-12Vdc voltages to the preamp channel. The 12Vdc wires from rail splitter to relays (two +/- conductors) and to preamplifier (three +/0/-conductors) will be in parallel.

BTW, with this +12V/-12V supply I still need to use 24Vdc relays, isn't it?

I already have Omron G6A-234-P-ST-US-24VDC, that I think are good quality. Have somebody experience with them, or with the others mentioned in my first post?

Thanks again.
Un saludo/Best regards
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Old 27th February 2008, 07:32 PM   #4
diyAudio Member
Join Date: Dec 2007
Location: Phoenix, AZ
Hola Jose,
You are correct in using 24vdc relays between the +12v and -12v pins of your power supply, the total voltage difference between these two pins will be 24vdc. You can still hook up the devices that require both +12v and -12v between the correct power pins and the ground pin of the power supply output.
I can't speak of the quality of the relays you are using, as I haven't used them, but I have used other Omron products in the course of my regular job. I don't recall ever having any problems with them, except those caused by human intervention.

Buena (Bueno?) Suerte,

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